It doesn't hurt to spy

I keep telling my husband that he needs to get up sometimes and go for a walk because that could be the cause that he is getting back pain. I really don’t like to argue with him every time I tell him this, but he would just tell me that he did walk and I just didn’t see him because I am very busy. Well, honestly I really don’t see him doing it, and there are times that I am not around and I couldn’t monitor his every moves. So I told him that if he will keep arguing with me I am going to get a spy camera, to record his every action. I really want him to be more motivated to get some exercise by himself, so that he will get stronger and gain back more strength. This is for his own good and I am just thinking about him.